Method of casting light metal alloys



Patented Dec. 4, 1923.

UNITED STATES 1,476,192 PATENT OFFICE.

B. VEAZEY, OF CLEVELAND, OHIO, AND EDWARD C. BUBDICK, OF MIDLAND, MICHIGAN, ASSIGNOBS TO THE DOW CHEMICAL COMPANY, 01 MIDLAND, MICHI- GAN, A CORPORATION OF MICHIGAN.

METHOD OF CASTING LIGHT METAL ALLOYS.

Jio Drawing. Appuoationnled November 88, 1921, Serial No. 517,949. Renewed April 5, 1928. Y

To all whom it may concern:

Be it known that we, WILLIAM R. Vmznx andEnwAno C. BURDICK, both citizens of the United States, and residents of Cleveland, county of Cuyahoga, and State of Ohio, and of Midland, county of Midland, and State of Michigan, respectrvely, have jointly invented a new and useful Improvement in Methods of Casting Light Metal Alloys, of which the following is a specification, the principle of the invention being herein explained, and the best mode in which we have contemplated applying that. principle so as to distinguish it from other inventions.

The present improvements relate more particularly to the casting of light metal alloys in which magnesium'is the predominant constituent, for example, an alloy such as described in U. S. Patent No. 965,485 to Pistor et 111., dated July 26, 1910, containing not less than er cent. of magnesium. By the same token the present improved method or process is, of course, adaptable to the casting of pure magnesium where such metal is handled by itself. The difliculties encountered in handling molten magnesium, vor an alloy largely composed of this metal, need not be emphasized. being well recognized, see for example, U. S.' Patent No. 906,820 to akowicz, dated December 15-, 1908. As best setting forth the state of the art in this connection, attention may further be called to the article by Dr. Ing. Felix Thomas in Stahl und Eisen, No. 40, page 290 (1920), which affords an authoritative descri tion of the casting of Elektron metal as evelgped by The Chemische Fabrik Griesheim Jlektron in Frankfurt.

According to the best known practice, as thus described b Dr. Thomas, such Elektron metal, whic is a trade-name applied by the manufacturer in question to a series of light metal alloys containing over 80 per cent. of magnesium with small additions of other meta s such as zinc, is melted in wrought iron or cast steel crucibles of limited capacity, such crucibles being closed while being heated in a suitable oven or furnace. Just as soon as all the metal in the crucible has been reduced to molten condition, the crucible is removed from the furnace and its contents poured. However, even where thegreatest precautions are taken, it is admitted that a slight overheating of the metal or other accidents are liable to cause the formation of a black oxide layer, as well as ignition of the mass of molten metal, and the article in question further describes the ste s to be taken to extin ish the flame in t e crucible if the metaflakes fire and to remove the oxide or nitride that results from contact with the atmosphere. Aside from the difliculties just referred to, the method in question involves leaving behind in the crucible a residuum of metal which has to be poured into an iron form and later again melted. The process, in other words, does not lend itself to continuous operation and considerable loss is entailed by thus rehandling the residual portions of the successive batches thus left behind in the crucibles and it is also rendered diflicult to maintain the proportion of alloyin constituents to accord with any prescribed formula.

One object of the present invention, accordingly, is to provide a method for casting light metal alloys ofthe class in hand, which will be relatively simple and permit of practically continuous operation for an extended period of time. A further object is to eliminate, to a large degree, the formation of the undesirable oxides and nitrides whereby not only is waste of the valuable ma esium metal avoided, but more perfect castings are secured than has heretofore been possible. To the accomplishment of the foregoing and related ends the invention, then, consists of the ste s hereinafter fully described and particu arly pointed out in the claims, the following description setting forth but one of the various ways in which the principle of the invention may be carried out.

According to our present improved method or process we employ, instead of a closed crucible in which to melt the magnesium or light metal alloy high in this metal, an open cast iron pot or equivalent suitable vessel in which the metal is melted along with a proper amount of flux, that while heavier than such metal, will have proper surface tension to properly and effectively coat the metal. As an example of such a flux, approximately equal parts of anhydrous magnesium chloride and sodium chloride may be employed, and if the specific gravity of such flux proves inadequate added. After the proper density of the fluxhas been established and a suflicient body of the molten metal accumulated, the casting is accomplished by directly ladling the metal from the mass floatin on the flux, as aforesaid, to the mold. 'Ihe particular character of the latter, whether a sand mold or permanent mold, e. g., of cast iron, is a matter of indifference so far as the present invention is concerned. In order thus to ladle the metal, the thin film of the flux that overlies the surface of the molten mass of metal in the pot is broken and brushed to one side so as to-uneover the clear metal and the ladle can then be filled and lifted before the film is re-established. Where proper precautions are taken, however, such re-establishment of the film will occur before any oxidation or other harmful effect is producedon the exposed metal and by .careful manipulation the operator is at the same time able to avoid taking up any of the flux in the ladle. The metal in the latter will, of course, be momentarily exposed to.

'floated in an adequate bath of flux' of the character described which serves to reserve the metal from direct contact with t e walls of the pot to which the-heating medium is applied.

he temperature of the molten mass of magnesium may furthermore be regulated by adding fresh stock metal to such floating mass from time'to time as the latter is diminished by ladling the metal to the molds. In other words, the mass of the molten metal may be maintained approximately constant and the operation in this way continued indefinitely; The referred temperature, as just indicated, wil be just a trifle above that at which the magnesium, or the particular alloy thereof that is being emgloyed, will melt.

ther modes of applying the principle of our invention may be employed instead of the one explained, change being made as re ards the method herein disclosed, provi ed the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invent1on:--

1. In a .nethod of casting magnesium and alloys thereof in which magnesium largely predominates, the step which consists in melting a quantity of the metal in an open vessel along with a quantity of flux that is heavier than such metal and has a surface tension when in molten state suflicient to cause same to coat the exposed surface of the metal, substantially as described.

2. In a method of casting magnesium and alloys thereof in which magnesium largely predominates, the step which consists in melting a'quantity of the metal in an open vessel along with a quantity of flux consisting of a mixture of magnesium chloride and an alkali metal chloride, such flux having a slightly higher specific gravity than such metal and a surface tension when in molten state sufficient to cause same to coat the exposed surface of the metal, substantially as described.

3. In a method of casting magnesium and alloys thereof in which magnesium largely predominates, the step which consists in melting a quantity of the metal in an open vessel along with a quantity of flux consisting of a mixture of magnesium and sodium chlorides in approximately equal proportions, such flux having a slightly higher specific gravity than such metal and a surface tension when in molten state suificient to cause same to coat the exposed surface of the metal, substantially as described.

4. In a method of casting magnesium and alloys thereof in which magnesium largely predominates, the step which consists in melting a quantity of the metal in an 'open Vessel along with a quantity of flux consisting of a mixture of magnesium and sodium chlorides in approximately equal proportions, with a relatively small amount of barium chloride added, such flux having a slightly higher specific gravity than such metal and a surface tension when in molten state suflicient to cause same to coat the exescribed.

osed surface of the metal, substantially as 5. In a method of casting magnesium and I alloys thereof in which magnesium largely predominates, the steps which consist in melting a quantity of the metal, floating same in a bath of flux, and then transferring metal from such floating mass to the mold as required.

6. In a method of casting magnesium and alloys thereof in which magnesium largely predominates, the ste s which consist in melting a quantit o the metal, floating same in a bath 0 flux, and ladling such metal from such floating mass directly to the mold as required.

7. In a method of casting magnesium and alloys thereof inwhich ma esium largely predominates, the steps melting a quantity of the metal in a suitable vessel together with a quantity of a flux" of slightly higher specific gravity, whereby w ich consist in I ill such metal is caused to float in a bath of such flux, and ladling such metal from such floating mass directly to the mold as required.

8. In a method of casting magnesium and alloys thereof'in which magnesium largely predominates, the steps which consist in melting a quantity of the metal in a suitable vessel together with a quantity of a ,flux of slightly higher specific gravity consisting of a mixture of magnesium chloride and an alkali metal chloride, whereby such metal is caused to float in a bath of such flux, and ladling' such metal from such floating mass directly to the mold as required.

9. In a method of casting magnesium and alloys thereof in which magnesium largely predominates, the steps which consist in melting a quantity of the metal in a suitable vessel together with a quantity of a flux of slightly higher specific gravity consisting of a mixture of magnesium and sodium chlorides in approximately equal proportions, whereby such metal is caused to float in a bath of such flux, and ladling such metal from such floating mass directly to the mold as required.

10. In a method of casting magnesium and allo s thereof in which magnesium largely predominates, the steps which consist in melting a quantity of the metal, floating the same in a bath of flux, ladling such metal from such floating mass directly to the mold as required, and adding fresh stock metal to 'such floatin mass as the amount of the latter is thus iminished.

11. A flux for us with molten magnesium and alloys thereof in which magnesium largely predominates, such flux consisting of amixture of magnesium chloride and an alkali metal chloride in approximately equal proportions with 'a relatively small amount of barium chloride added to raise the specific gravity of such flux slightly A abov that ofthe metal.

12. A flux for use with molten magnesium and alloys thereof in which magnesium large-1y predominates, such flux consisting of a, mixture of magnesium and sodium chlorides in approximately equal proportions with a relatively small amount of barium chloride added to raise the specific gravity of such flux slightly above that of the metal.

Signed by me this 21st day of November,

WILLIAM R. VEAZEY. Signed by me this 23 day of November,

EDWARD C. BURDICK. 

